A therapeutic approach termed "virus-directed enzyme prodrug therapy" (VDEPT) has been proposed as a method for treating tumour cells in patients using prodrugs. Tumour cells are targeted with a viral vector carrying a gene encoding an enzyme capable of activating a prodrug. The gene may be transcriptionally regulated by tissue specific promoter or enhancer sequences. The viral vector enters tumour cells and expresses the enzyme, in order that a prodrug is converted to an active drug only in the vicinity of the tumour cells (Huber et al, Proc. Natl. Acad. Sci. USA (1991) 88, 8039).
Although the VDEPT system enhances the concentrations of anti-tumour agent which may be delivered to the site of a tumour, there is still a need to enhance the specificity and efficiency of drug delivery.
The present invention addresses such problems by the use of a VDEPT viral vector which encodes for a nitroreductase.